1 Field of the Invention
The present invention relates to a stent for implantation in a body lumen and, more particularly, to a stent that is designed to, when it is implanted in the body lumen, enhance its reliability and minimize the medical side effect by assisting the function of the body lumen and preventing the inverse current of food or fluid input in the body. The present invention further relates to a method for manufacturing such a stent.
2 Description of Prior Art
Stents are generally tubular-shaped devices which function to hold open a segment of a blood vessel or other anatomical lumen. They are particularly suitable for use to support and hold back a dissected arterial lining which can occlude the fluid passageway therethrough.
A variety of stents are well known in the art. The stents are classified in an elastic stent and a plastic stent. The former is designed to be contracted by outer force and to be self-expanded when the outer force is released. The latter is designed to keep its deformed state unless outer force is applied thereto.
The stent is required to perform various functions according to a location of the body lumen it is to be implanted. For example, there is a sphincteral muscle for the esophageal orifice on a connecting portion of the stomach and the esophagus. The sphincteral muscle prevents the food and fluid from reversely flowing. Therefore, when the stent is implanted on the sphincteral muscle, the sphincteral muscle loses its inverse current preventing function. Therefore, the stent to be implanted on the sphincteral muscle for the esophageal orifice should be provided with means for preventing the inverse current, thereby preventing the medical side effect caused by the inverse current of the food and fluid.
A variety of prior art stents having the inverse preventing means can be found in U.S. Pat. Nos. 3,755,823, 4,580,568, 5,840,081 and 6,168,614.
However, since the prior art stents having the inverse preventing means have short valve plates integrally coupled on an inner circumference of the stent, the valve plates may be deformed or warped by outer force when the stent is implanted in the body lumen, making the valve plates opened regardless of the supply of the food and fluid input.
Furthermore, the inverse current preventing means disclosed in the prior art stents has valve plates that should be bonded on the inner circumference of the stent by adhesive, requiring a bonding space for the bonding process to make it difficult to manufacture the same.
In addition, a prior art stent having the inverse current preventing means that is formed on an outer circumference of the stent is also proposed. However, since the inverse current preventing means stimulates the inner wall of the stomach, a medical problem may occur.